For years, staff and visitors at Discovery Green have seen a large fish swimming in the park's 1-acre lake.

"If you walk along the pier, the fish would follow you, like a dog or a pet," says William Flowers, the park's site manager. "They really became part of the culture."

The arrival of the fish is one of the park's greatest mysteries, as the concrete-bound lake was never actually stocked with fish. But while there were several fish calling Discovery Green home, one larger-than-life koi emerged as a fan favorite.

"We started calling him Big Poppa because he was bigger than the bass and all the other goldfish," says Flowers.

He'd slip away from view for days at a time as he rested among the muck in the lake's bottom, a habit of koi. The longer he returned to his bottom-feeder habits, the higher tensions grew among his fans.

"After a few days, when we'd see him, we'd be like, 'Yay!' We'd have fish die every once in a while - turtles would get them or something - but we were always afraid that it would be him," says Flowers. "And he was a favorite - the only fish that had a name."

Big Poppa has called Discovery Green home for at least six or seven years (maybe someone set him free in there, or maybe a bird dropped him, Flowers speculates). But earlier this month, the park had to drain the lake to repair a leak. That meant catching Big Poppa.

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What's the difference between koi and goldfish?

Koi (Cyprinus carpio) and goldfish (Carassius auratus) are both in the same family: Cyprinidae. All koi have the same body type and can vary in color. They can also grow up to 2 to 3 feet in length. Most goldfish are orange, with a few types that also have black, white and calico coloring. They come in a variety of body shapes and stay relatively small in size.

How big do koi get?: Japanese koi usually grow 22 to 26 inches long. Jumbo-size koi grow up to 36 inches long.

"Slowly, over the course of about two weeks, our operations team netted the fish and put them in their own containers, very carefully," says Ren Mitchell, a marketing manager for the park.

They constructed aerated systems to help the fish breathe in their containers, and made plans to relocate them to Katy to live in a retirement pond, since a pH change in the park's lake water could have far-reaching health consequences for Big Poppa and others.

This meant a chance to see the usually slippery Big Poppa up close. And Mitchell couldn't believe her eyes.

"We knew he was big. But we didn't know exactly how big he was," she says. "We'd been visually guesstimating. But he filled up - from tip to tail - an entire Tupperware box."

He had to have been more than 2 feet long, she says.

"He was super big and super heavy. I'm not sure, but he had to have been close to 100 pounds."

Really?

"Maybe 60," she couches. Flowers would know better.

"I didn't measure him," says Flowers. "I honestly was trying to be as gentle and careful with him as I could. But we bought some heavy-duty storage tubs, and they're about 2-and-a-half feet long, and that's about how long he was."

But what about weight?

"If I had to guess, I'd say he was probably 20 pounds," he says. "Yeah, about 20 pounds."

The folks at Nelson's Water Garden in Katy, who took Big Poppa in, would likely have a better estimate, he says.

Mary Gonzales, the indoor manager at Nelson's, has seen plenty of koi fish in her day. At the shop, there's a koi pond next to a gumball machine stuffed with fish food, where customers drop a quarter before sprinkling fish treats on the water's surface. The result is a school of koi who have grown big, fat and happy over the years. But even these guys have nothing on Big Poppa, she says.

"It took two guys to pick him up when he arrived," she says. "And that was with the water in the container as well, which throws off the exact weight."

So she doesn't have an estimate on what he weighs. And they didn't risk pausing to measure him before sliding him into the waters of her home-based retirement pond, where he's chilling with perch, bass and minnows.

"He was really stressed from the move, so we did our best to get him out as quickly as we could," says Gonzales, a fish expert whose parents own the water garden where she works.

But she got an eyeball on him, up close and personal. And one thing's for sure:

"He's one of the biggest koi we've ever seen," she says. "Three-and-a-half feet."

Maggie Gordon is the assistant features editor at the Houston Chronicle, where she has worked since 2015.

Before joining the Chronicle, Maggie worked at papers in Connecticut, including the Stamford Advocate and the Greenwich Time, covering a variety of beats, from general assignment and municipal coverage to education, demographics and business reporting including real estate trends and the hedge fund industry. She is a graduate of the S.I. Newhouse School of Public Communications at Syracuse University.

Greatest hits include a narrative about alligator hunting in a Texas bayou, a horse trainer's quest to tame a wild mustang in one summer, and a feature about the inmates in a transgender tank for sex workers in Houston's county jail. She loves quirky characters and stories that combine adventure and humanity. Bonus points if it unearths a love story.